This is often a common question asked. I am glad that someone had presented it to me as it is often easy to discuss it without having given much thought to the source.
The federal government through a cooperation between the Government Service Agency (GSA), National Aeronautic Space Agency (NASA), and the Department of Defense (DoD) have created the Federal Acquisition Regulations (FAR), and with some variation specific to the DoD the D-FAR. These are codified in the US Code as 48 CFR Chapter 1. You may the entire document at http://acquisition.gov/far/index.html, the GPO FDsys at http://www.gpo.gov/fdsys/browse/collectionCfr.action?collectionCode=CFR, or the eCFR at www.ecfr.gov (my personal favorite).

States may have their requirements buried in a plethora of locations and this varies frequently from state to state. I have found though that google is often a great guide to finding where these regulations may be hidden in statute. However, as a practical matter and in achieving a big picture process and form, one can usually get by with a solid understanding of the American Bar Association Model Procurement Code. The current print version available from the ABA is from 2000 and is currently under revision. This code has been adopted in some form from most state and local jurisdictions in an effort to provide some uniformity. Of important note though is that there is a 2007 version specific to infrastructure procurement. Both can be found by clicking here.

As a good Texan I would be doing a severe disfavor in not identifying the source of contracting provisions in the local statutes. While many municipalities and political subdivisions have enacted a truly local version the core of applicable regulates are found in the Texas Local Government Code Chapter 8. The state itself has its purchasing regulations codified in the Texas Government Code Title 10(d)(2155 – 2158).
To try and capture all of the uniqueness that is stored within these regulations and statutes is nearly impossible, so for specific questions it is best to contact a government procurement specialist or attorney that specializes in this area.